1. Field of the Invention
The present invention relates to control systems and methods in general and, more particularly, to control systems and methods for oil refining units.
2. Summary of the Invention
A solvent refining unit treats medium sour charge oil with an N-methyl-2-pyrrolidone solvent, hereafter referred to as MP, in an extractor to yield raffinate and extract mix. The MP is recovered from the raffinate and from the extract mix and returned to the extractor. A system controlling the refining unit includes a gravity analyzer, a sulfur analyzer, a refractometer and viscosity analyzers. The analyzers analyze the medium sour charge oil and provide corresponding signals. Sensors sense the flow rates of the charge oil and the MP flowing into the extractor and the temperature of the extract mix and provide corresponding signals. The flow rate of the medium sour charge oil or the MP is controlled in accordance with the signals provided by all the sensors, the refractometer and the analyzers while the other flow rate of the medium sour charge oil and the MP flow rates is constant.
The objects and advantages of the invention will appear more fully hereinafter from a consideration of the detailed description which follows, taken together with the accompanying drawings wherein one embodiment of the invention is illustrated by way of example. It is to be expressly understood, however, that the drawings are for illustration purposes only and are not to be construed as defining the limits of the invention.